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Subject: Re: start switching sysfs attributes to expose the seq_file
To:     Christoph Hellwig <hch@lst.de>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "Rafael J. Wysocki" <rafael@kernel.org>,
        Alexander Viro <viro@zeniv.linux.org.uk>
Cc:     Jens Axboe <axboe@kernel.dk>, Tejun Heo <tj@kernel.org>,
        linux-block@vger.kernel.org, linux-xfs@vger.kernel.org,
        linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
References: <20210913054121.616001-1-hch@lst.de>
From:   Bart Van Assche <bvanassche@acm.org>
Message-ID: <21413ac5-f934-efe2-25ee-115c4dcc86a5@acm.org>
Date:   Mon, 13 Sep 2021 09:39:56 -0700
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On 9/12/21 10:41 PM, Christoph Hellwig wrote:
> Al pointed out multiple times that seq_get_buf is highly dangerous as
> it opens up the tight seq_file abstractions to buffer overflows.  The
> last such caller now is sysfs.
> 
> This series allows attributes to implement a seq_show method and switch
> the block and XFS code as users that I'm most familiar with to use
> seq_files directly after a few preparatory cleanups.  With this series
> "leaf" users of sysfs_ops can be converted one at at a time, after that
> we can move the seq_get_buf into the multiplexers (e.g. kobj, device,
> class attributes) and remove the show method in sysfs_ops and repeat the
> process until all attributes are converted.  This will probably take a
> fair amount of time.

Hi Christoph,

Thanks for having done this work. In case you would need it, some time ago
I posted the following sysfs patch but did not receive any feedback:
"[PATCH] kernfs: Improve lockdep annotation for files which implement mmap"
(https://lore.kernel.org/linux-kernel/20191004161124.111376-1-bvanassche@acm.org/).

Bart.